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tiaccadi
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V7 replication with excluded disk

Post by tiaccadi » Oct 18, 2013 8:57 am

Hello,
I deployed a B&R V7 environment, in order to replicate our vSphere infrastructure to the DR site (WAN link = 8 Mbit/s)

I started to replicate VMs (entire VMs, so all disks selected), but my WAN link speed causes me some trouble because of the amount of data

I tried excluding the system disks from the weekdays replication jobs (they don't change too much, but enough to cause those troubles), in order to reduce delta footprint
Now the jobs are able to finish during the weekdays nights

However, I want to replicate the entire VMs during the weekends, in order to have at least 1 week RPO for system disks

Which is the best way to achieve this?

To be more practical: I have a weekday job (monday to thursday) for disk scsi0:1, with 7 replica points
What happens if I add a weekend job (friday night) for scsi0:1 AND scsi0:0 (system disk) with 7 replica points? Does it work?
What happens to replica points? And to VMware VMDKs and snapshots in the DR site?

More important: if I want to failover to a point-in-time located during the weekday, I guess I'll have to failover the weekday replica.. will the replica came up with the latest system disk available?

Vitaliy S.
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Re: V7 replication with excluded disk

Post by Vitaliy S. » Oct 18, 2013 9:45 am

Hello,
tiaccadi wrote: To be more practical: I have a weekday job (monday to thursday) for disk scsi0:1, with 7 replica points
What happens if I add a weekend job (friday night) for scsi0:1 AND scsi0:0 (system disk) with 7 replica points? Does it work?
What happens to replica points? And to VMware VMDKs and snapshots in the DR site?
Adding virtual disks to already configured replication should not cause any issues. Your job will continue running normally, but you will have different number of restore points available for your disks. BTW, keep in mind that you cannot use two jobs pointed to the same target replica, so it will be another VM or you will have to change your job configuration every week.
tiaccadi wrote:More important: if I want to failover to a point-in-time located during the weekday, I guess I'll have to failover the weekday replica.. will the replica came up with the latest system disk available?
You will have to failover to the state when system disk was replicated, otherwise your VM will not boot.
tiaccadi wrote:Which is the best way to achieve this?
Your current approach seems too complex to me, cause you will have to deal with adding/removing virtual disks from the replication job. If I were you, I would just use backup files to pre-seed your replication job and then transfer only changes during all runs.

Thank you!

tiaccadi
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Re: V7 replication with excluded disk

Post by tiaccadi » Oct 18, 2013 10:17 am

Vitaliy S. wrote:Adding virtual disks to already configured replication should not cause any issues. Your job will continue running normally, but you will have different number of restore points available for your disks. BTW, keep in mind that you cannot use two jobs pointed to the same target replica, so it will be another VM or you will have to change your job configuration every week.
I guess I'll have to change the configuration job every week, so.. :cry:

However, what are the consequences to use two jobs pointed to the same target replica?

I just did a small test (two new jobs, replica seeding enabled), and it seems that every job remove the restore points of the other one (it consolidates all its snapshots)
The ready replicas then shows inconsistent information (there're two ready replicas for that VM, but restore points are wrong), and I think it's not a great thing :D
Vitaliy S. wrote:You will have to failover to the state when system disk was replicated, otherwise your VM will not boot.
Why? I did a test with a VM: system disk replicated 1 week ago, data disk replicated every day
I start a failover to yesterday, and the VM booted up: files on system disk are 1 week old, files on data disks are 1 day old
Vitaliy S. wrote: Your current approach seems too complex to me, cause you will have to deal with adding/removing virtual disks from the replication job. If I were you, I would just use backup files to pre-seed your replication job and then transfer only changes during all runs.
VMs have been already pre-seeded, some full replications have been already made
But I wanted to remove some data from replication during the weekdays, replicating systems disks only on weekends

I guess I've to add and remove disks from exclusion list manually.. or is there a way to do this via powershell?

Meanwhile, thank you so much Vitaliy S.

Vitaliy S.
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Re: V7 replication with excluded disk

Post by Vitaliy S. » Oct 18, 2013 10:39 am

tiaccadi wrote:However, what are the consequences to use two jobs pointed to the same target replica?
Well...you have pinpointed the consequences pretty well in the post below ;)
tiaccadi wrote:I just did a small test (two new jobs, replica seeding enabled), and it seems that every job remove the restore points of the other one (it consolidates all its snapshots)
The ready replicas then shows inconsistent information (there're two ready replicas for that VM, but restore points are wrong), and I think it's not a great thing :D)
tiaccadi wrote:Why? I did a test with a VM: system disk replicated 1 week ago, data disk replicated every day
I start a failover to yesterday, and the VM booted up: files on system disk are 1 week old, files on data disks are 1 day old
Depends on the application you have inside the Guest OS, I have recently tried this trick with my SQL Server and 3rd party application and my application didn't work :)
tiaccadi wrote:VMs have been already pre-seeded, some full replications have been already made
But I wanted to remove some data from replication during the weekdays, replicating systems disks only on weekends

I guess I've to add and remove disks from exclusion list manually.. or is there a way to do this via powershell?
I think that should be possible, please search our PoweShell subforums, as far as I remember there was a script example for this procedure.

Hope this helps!

v.eremin
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Re: V7 replication with excluded disk

Post by v.eremin » Oct 18, 2013 10:59 am

As mentioned, the scenario you’re talking about doesn’t seem to be a good and reliable one. Though, if you still want to stick with it, you can use the script proposed in this topic; should answer your requirements.

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